Dial knobs



M. W. BANG March 6, 1956 DIAL KNOBS Filed Aug. 6, 1953 Fig.

INVENTOR. MOGENS W. BANG ATTORNEYS United States Patent DIAL KNOBS Mogens W. Bang, Montclair, N. J., assignor to Allen B.

Du Mont Laboratories, Inc., Clifton, N. .I., a corporation of Delaware Application August 6, 1953, Serial No. 372,641

2 Claims. (Cl. 116--124.4)

This invention relates to dial knobs and related indicia and markings as for electrical instruments and, more particularly, to those devices utilizing concentric inner and outer control shafts independently adjustable, and dial knobs therefor.

Dual knob construction employed in the past, containing indicia, has involved a problem of parallax error since, in prior art construction, the smaller or so-called inner knob is displaced from the control panel and the markings thereon correspondingly are displaced from indicia on the panel. Accordingly, it is an object of this invention to provide an arrangement which will reduce or minimize parallax error.

In the drawings, Fig. 1 is a plan view of a pair of concentrically mounted control knobs and a control panel, together with indicia on each thereof, and Fig. 2. is a. sectional view through 22 of Fig. 1.

In accordance with this invention the larger or so-called outer knob is made of transparent material such as clear plastic and contains an inner hub portion fitted around a control shaft on which the knob is mounted, a laterally extending substantially flat central portion, and an outer longitudinally extending rim portion. The outer or n'm portion is that which may be gripped by the operator in making necessary adjustments of the controls. Indicia on the control panel is visible through the transparent laterally extending flat portion of the knob.

A second smaller or so-called inner knob is mounted on a concentric and extending inner control shaft. The inner knob has a cutaway portion which concentrically or coaxially extends over the inner hub portion of the outer knob with the inner end thereof extending closely adjacent the central fiat portion of the outer knob.

Referring to the drawings, the outer knob 11 and the inner knob 12 are mounted in any well known manner on their respective concentrically extending control shafts 13 and 14, respectively. The control shafts 13 and 14 extend through a control panel 15 and may connect to mechanisms such as electrical switches, potentiometers or variable condensers, etc. (not shown).

The outer knob 11 has a longitudinally extending hub portion 21 for mounting on its control shaft 13. The outer diameter of the hub 21 is made as small as possible providing necessary mechanical strength to support the knob 11 on its control shaft 13. Neither the diameter thereof nor the longitudinal extension thereof is critical and may be made to desired size. The laterally extending flat portion 22 extends from the hub 21 to an outer longitudinally extending rim portion 23. The rim portion 23 provides the necessary gripping portion for control of the knob.

The inner knob 12 has a central longitudinally extending bore 32 for securing the knob to its concentrically extending shaft 14 in any well known way. The inner or open end of the knob 12 has a larger bore portion 33 which encompasses concentrically the hub 21 of the outer knob 11 with necessary space therebetween to permit rotation of the knobs 11 and 12 independently of one another. The inner end of the knob 12 extends closely adjacent to the centrally fiat portion 22 of the knob 11, again with necessary spacing to permit the independent rotation of the knobs.

Two sets of indicia are provided on the control panel 15 as indicated at 16 and 17. These respective indicia provide the necessary readings for the respective mechanisms of the control shafts 13 and 14. A marker indicia 18 is provided on the outer side of the rim 23 of the knob 11 and preferably along a flange or skirt portion extending slightly outwardly therefrom, as shown. The marker 18 on the knob 11 thus lies closely adjacent the indicia 16 on the panel 15 thus making possible the necessary readings without parallax error.

Similarly a marker indicia 19 is provided longitudinally along the outer surface of the control knob 12 terminating at the inner end thereof closely adjacent the centrally flat portion 22 of the outer knob 11 and, preferably as before, along a small flange or skirt portion as shown. In this way the marker 19 is closely adjacent the indicia 17 on the panel 15.

The indicia 17 is visible through the clear plastic or transparent skirt portion 22 of the outer knob 11. The close proximity of the marker 19 on the knob 12 to its corresponding indicia 17 on the panel 15 substantially eliminates or effectively reduces greatly parallax error. It will be noted that this reduction in parallax error is made possible by the concentric arrangement of the inner knob 12 about the hub 21 of the outer knob 11, thus making possible the extension of the marker 19 closely adjacent to the panel 15. The marker 19 is spaced from its corresponding indicia 17 only by the thickness of the transparent plate or flat portion 22 of the outer knob 11.

As shown, the panel 15 may, if desired, be made of a light transmitting material and a source 20 of illumination may be provided to cause the indicia 16 and 17 to show clearly against a lighted background.

While a preferred embodiment of the invention has been described, the scope thereof is covered by the following claims.

What is claimed is:

1. In a concentric knob assembly, a pair of concentric shafts comprising an inner and an outer shaft, a panel through which said shafts protrude, a first knob having a hub affixed to said outer shaft, said knob being made of clear plastic and being of dish-shaped form having a hub and a rim portion extending coaxially and a substantially flat central portion extending laterally between said hub and said rim portion, said rim portion bearing an indicia mark, a second knob aflixed to said inner shaft and having a hollowed out portion positioned over said hub, a skirt portion extending forwardly to said flat central portion of said first knob and bearing an indicia mark, said panel having a first set of indicia thereon in concentric alignment with the indicia mark of said first knob and a second set of indicia in concentric alignment with the indicia mark of said second knob, said second set of indicia being visible through the clear plastic flat central portion of said first knob.

2. The device of claim 1, in which said panel is transparent and a source of illumination is provided to make said indicia visible.

References Cited in the file of this patent UNITED STATES PATENTS 2,220,590 Vogt Nov. 5, 1940 2,498,835 Brotman Feb. 28, 1950 2,572,023 Goodwin Oct. 23, 1951 

